Can I create pbr textures from blender and export it to Unreal or Unity?
"PBR" is a buzzword that refers to some shader design conventions, such as respecting energy conservation, using fresnel reflections, and such. "PBR Textures" are merely textures intended for some shader that follows these conventions. As Cycles is a render engine itself and not a texture authoring tool, it won't be helpful in authoring textures. You can certainly paint textures using Blender's texture painting function that target a PBR shader, but as Blender doesn't have a PBR viewport shader you will won't have the instant viewport feedback of how your textures are looking. You have to export them out to your game engine, doing some "guess and check" with the values.